One more thought that I cannot find an answer to through Google.
InReach will continue to send a message until it reaches an Iridium satellite.
How many times will the SatPaq continue to transmit a message until its completed?
And if the user is stationary due to medical emergency then a fixed satellite will never move into Line of Sight. It will be 100% dependent on the user moving to a unobstructed position.
If I'm understanding the manual correctly, it doesn't continue to try to transmit.
If connectivity is unavailable it queues the message and then reminds you every 10 minutes to push the send button again. Pushing the send button starts the aiming process.
If the compass isn't calibrated, the aiming process starts with rolling a ball around the screen to calibrate the compass (so it knows where to tell you to point the Satpaq)
After you send a message, you have to check for replies, i.e., aim the device at the right place in the sky and press the Check Messages button (on the app) to retrieve the reply. There is no notification on the app that a reply is waiting.
(Note- I'm assuming the user is out of reach of wi-fi and cell connectivity. If those are available and the Satpaq isn't set to Satellite Only, it will use those before attempting satellite connectivity)